The following patents and articles showing treatments for deactivated catalyst to recover their hydrodesulfurization activity properties, were taken as basis of non-oxidative alternatives to retrieve HDS activity of deactivated catalysts:
U.S. Pat. No. 4,863,884 protects a method to rejuvenate (1) deactivated catalysts used, in this case, a spent hydroprocessing catalyst of heavy hydrocarbons oil which contains 10-40% weight of adsorbed hydrocarbon and 4-10% weight of contaminating metals (Ni+V). The first washing step was carried out with toluene at a superficial velocity of 0.4 feet/second in upward flow, for 4 hours to dissolve all the heavy hydrocarbon adsorbed on the catalyst used, the end system is purged at a pressure of 1-5 psi to evaporate all the solvent and obtain a catalyst free oil which has the following characteristics: Carbon 16.3 wt %, 13.6 wt % sulfur, 1.3 wt % nickel, 6.0% vanadium weight. This catalyst was subjected to a second washing treatment using a 15 weight-% solution of H2SO4 up flow at a rate of 0.4 ft/sec for one hour. The third step was a water washing at a space velocity of 4 h−1 after which the catalyst is dried at 121° C. And after drying, the reactivated catalyst can be used again as a catalyst in the hydrotreating process of heavy oil fractions.
U.S. Pat. No. 5,230,791 discloses a process for reactivating deactivated hydrotreating catalysts (2) alumina supported. The treatments protected by this invention comprise three stages, the first is treatment with solvent, toluene at a temperature of 93° C. for 4-12 hours followed by air drying at 110° C., then the catalyst is dried at room temperature under vacuum. The following treatment involves the washing with organic solvents from the following group: 1methyl 2-pyrrolidinone, quinolone, n-methyl pyrrolidone, phenol, furfural and their mixtures, heated since 93° C. to 260° C. with treatment periods: 1-12 hours. A slight degree of recovery is observed after 4 washing cycles with these solvents. Regenerating the catalyst after washing is also performed using a mixture containing 1-6% volume oxygen in an inert gas at temperatures from 371 to 482° C.
U.S. Pat. No. 5,254,513A presents a method for the reactivation of deactivated H-Oil catalysts (3) alumina supported, the deactivated catalysts in this process have carbonaceous and metallic deposits and they can be reactivated. A solvent washing is performed to remove process oil, followed by treatment with steam at temperatures of 1000-1250° F. (538-677° C.), the resulting catalyst can be reused in a process of catalytic hydrotreating. Optionally the treated catalyst can be regenerated in the presence of oxygen at 700° F. (371° C.). There are three steps of reactivation: a) removal process oil by washing with hydrocarbon solvents such as toluene, naphtha at 120° C. and dried to obtain an oil-free catalyst; b) contacting the washed catalyst at the previous step with water vapor and c) recovering a reactivated catalyst supported on alumina steam treatment zone for 3-5 hours. Also it included in the patent cases oxidative regeneration at 371° C. in the presence of an oxygen mixture (1.6 wt %) in nitrogen to transform carbonaceous deposits in CO2. The recovery of HDS activity was measured using a model reaction, benzothiophene hydrodesulfurization and recovery obtained by the steam treatment was measured by the HDS conversion was 11.4 wt-% when the catalyst is steamed at 1200° F. for three hours, obtaining an atomic ratio H/C of 0.44.
U.S. Pat. No. 5,445,728 presents the reactivation of a deactivated catalyst HDS-1443B (4) from H-Oil Unit of Criterion Co., which consists of three steps of catalyst treatment:
First, remove the adsorbed hydrocarbon to obtain clean catalyst particles, treatment with steam at temperatures of 537-677° C. and catalytic regeneration @482° C. in a stream of 1.6 volume-% of oxygen diluted in nitrogen. The first step removes adsorbed hydrocarbons in the boiling bed reactor, these can be cleaned intermittently or continuously with liquid hydrocarbon solvent to remove the oil from the process. It can be performed in two ways, the deactivated catalyst can be added to a tank of liquid solvent with stirring, or in a vertical column of liquid solvent may be fed in ascending order, with uniform flow. In both forms washing liquid solvent may be naphtha, toluene and mixtures thereof, the system can be heated to 200-300° F. (93-148° C.), then dried at 250° F. (120° C.) air under vacuum. An alternative approach may be to introduce a flow of nitrogen at high temperature, greater than 500° F. (over 260° C.) until the oil is removed from the process.
U.S. Pat. No. 5,906,953 protects rejuvenation treatment (5) of a deactivated catalyst from CRITERION Company (HDS-2443B) using a vacuum residue from Mexican crude Isthmus/Maya containing 27.8 wt % Carbon Conrradson with an API gravity 4.5, containing 4.2 wt % sulfur and 0.7 wt % nitrogen, with a ratio [C/H] of 8.42, 475 wt-ppm of vanadium and 91 wt-ppm of nickel and 25.3 wt % of insoluble compounds in pentane. This catalyst was reactivated using three steps comprising: first deactivated catalyst is washed with an organic polar solvent which is soluble in both oil and water, acetone is preferred because of its low cost, availability and easy recovery after washing. The space velocity used in this step were 1.5 to 3.0 h−1 at atmospheric pressure and a temperature between 32 and 65° C. for 2 hours, it was required a second washing with solvent and then two more water washing. The second washing step corresponds to the removal of metal contaminants using a solution of 10-20 weight-% concentration H2SO4 effectively removes 30 to 40% by weight of nickel and vanadium deposited on the catalyst, and it is performed twice. Involvement of the active metal phases [Nickel-Molybdenum] is 4% maximum and aluminum in the support 6% maximum. After this treatment two washes with fresh water are required to complete the removal of the acid solution. Subsequently the third treatment is burning coke at 399-454° C. in atmosphere containing oxygen 1-20%, after this final treatment the reactivated catalyst is obtained. The recovery of activity was 90% after the first washing solvent and with sulfuric acid, and after the second wash was achieved 100% activity, based on the data of the fresh catalyst (100%) and considering that deactivated catalyst (0%).
U.S. Pat. No. 6,843,813 B1 protects a cleaning treatment of catalytic mufflers (6) using the following solvent mixture: fifty percent by volume of xylene, twenty percent by volume of acetone and twenty percent by volume of 2-propanol and ten percent by volume of a paraffinic hydrocarbon. This mixture is considered a cleaning composition or rejuvenation of a catalytic converter for treatment with gas and light hydrocarbons, or by the use of vaporizable liquids on deactivated catalysts in removing combustion emissions in automotive vehicles. Treatment does not require disconnecting the catalyst of the engine, fuel can be replaced by the mixture mentioned above, operating at 60-90° C. temperature is achieved rejuvenate the catalyst, improving performance of reducing toxic emissions. Emissions of greenhouse gases are modified muffler off to the muffler reactivated as follows: CO of 2.9 to 0.03 wt %, hydrocarbon from 226 to 24 weight-ppm, CO2 rises from 12.9 to 15.1 weight-% to 2500 RPM, so this treatment is considered effective for this type of deactivated catalysts.
US patent application (6) number 20090261019 considered removing contaminants by washing with solvents followed by treatment of mild regeneration. During regeneration, the washed catalyst is contacted with a gas containing oxygen at an elevated temperature. In various treatments, the temperature during regeneration is at least 300° C., 350° C. and less than 500° C.
Some efforts have been reported to eliminate contaminants of deactivated catalysts, as an alternative enhancement of catalytic activity by catalyst pore unlocking and removing surface contaminants from the active sites. In this patent indicate the initial treatments to these deactivated catalysts consist remove adsorbed hydrocarbons and carbon on the catalyst. The first part of this treatment uses a xylene aromatic compound, for example, followed by a non-polar solvent, cyclohexane and finally another polar solvent such as acetone. Pollutant removal solvent can combine the action of various solvents of different nature, to remove various types of hydrocarbons more effectively. In addition to these solvents stream on the deactivated catalyst, a flow of stream gas is fed simultaneously. This gas must be inert in contact with the deposited carbon and the catalyst, it is generally used nitrogen, which also drag the solvent, coke, water, noble gases and carbon dioxide.
Mohamadbeigy et al (7) reported a method of rejuvenating deactivated catalyst hydrodesulfurization (HDS). The discussion focuses on regeneration of porous catalysts containing alumina as a substrate or base, which it was deactivated during hydrodesulfurization process, the metal contamination is removed by acid treatment. Initially the deactivated catalyst is rinsed with naphtha to remove hydrocarbons and placed in an oven at 120° C. for 24 hours to dry. After this step, the acid washing is performed to remove metal contaminants. Acetic acid is used with different molarities (0.05, 0.10, 0.2 and 0.3M) for this purpose. Acetic acid is placed in a Soxhlet extraction equipment and heated to boiling, the vapors rise through an outer chamber and condense and fall to the bottom of the Soxhlet chamber.
The results of the experiments rejuvenation HDS catalysts show that the deactivated catalyst can be reused in hydrotreating processes. Research aimed at the removal of nickel and vanadium compounds from the surface and pores of HDS deactivated catalyst and in turn improve the BET area without significant removal of the base alumina, through the selection and control of process steps.
Abdullah et al (8) studied optimum conditions for extraction of deactivated catalysts by accelerated extraction techniques and equipment using Soxhlet extraction. The research was carried out to evaluate two methods of extraction: the conventional type Soxhlet extraction and accelerated solvent extraction (ASE). Extracting deactivated catalysts with a number of solvents with gradually increasing polarity is a function of extraction time and the properties of the extraction solvent. In both methods, the deactivated catalyst was successively extracted with n-heptane, toluene, tetra hydrofuran and dichloromethane. Nuclear magnetic resonance (NMR)13C were used to study both the coke solubility and insolubility of carbon on the catalyst surface. The study was found that ASE extraction method was superior since it reached less than 5 minutes after solvent extraction the same extraction efficiency than conventional Soxhlet extraction, which requires 6 to 12 hours of extraction.
The article Menoufy et al (9) refers to studies for rejuvenation, metal recovery and re-use of NiMo—Al2O3 catalysts used in the refining of waste lubricating oil. The study included washing the deactivated catalyst extrudate NiMo-A12O3 type (containing 8.5 wt % carbon, 4.05 wt % S and 11.55% weight Si) using a soxhlet equipment to remove residual lubricating oil, and then first naphtha with toluene. So far, the researchers reported that the catalyst is considered clean of hydrocarbons containing only C, S and metals; It was dried at 120° C. for 24 hours. Then this dry spent catalyst to a sealed flask and dipped in carbon disulfide (100 ml/10 g) at room temperature, stirred for 12 hours, filtered and dried in air at room temperature. The catalyst was calcined using an electric furnace at 450° C. (25° C./min) for 20 hours at constant temperature to eliminate residual carbon and sulfur.
Subsequently, the procedure was performed to rejuvenate the catalyst by leaching. The experiment was performed in a conical flask fitted with reflux condenser at high temperature (100° C.) immersed in a water bath. 10 g of catalyst were placed (extruded, comminuted, with and without charcoal) in a mixture of 4% oxalic acid previously oxidized with 5% H2O2. Of the crushed samples were recovered higher metal quantities than in extrudate samples. This is because in crushing, the blocked pores of the catalyst are open and the metals found in these pores are more exposed to the solution by the leaching agents.
Metal recovery carbonless catalysts was greater as the concentration of bleaching agent compared to catalysts with coke increased. This difference was attributed to the oxidation states of the metallic species. The metal catalysts carbonless were at their highest oxidation state, which favored the formation of soluble complexes M oxalate (C2O4) X which impacted the leaching rate, whereas catalysts with carbon, the metals were as sulfides, lower oxidation state. It is likely that in the presence of H2O2, lower valence metals in the catalysts with carbon, they were oxidized and the total of metals were complexes, so leaching rate was based on the amount of metal ions formed.
Because the grinding process increase the cost involved in the recovery of metals, only extrudates were considered for this purpose. Mo and Ni mainly recovered in addition to P, Zn, Fe, Mg, Ca, Na, K and Si after leaching in different concentrations. Only silicon (SiO2 by XRD and XRF) presented recovery difficulty, increase the difficulty as your concentration is increased in the deactivated catalyst. The catalyst remained with 12.71% of Si after leaching with 4% oxalic acid. Analysis of selective recovery of metals observed that recovers more Mo than Ni. Furthermore, the nickel atoms located in the tetrahedral sites of alumina could be removed by leaching and redistributed on the remaining layer of molybdenum, enhancing their interaction even in presence of silica which is bound to Alumina and it was favored the formation of precursors for Mo—Ni—S, when was carried out with 4% of oxalic acid.
The effect of leaching with 4% of reagent on the textural and mechanical properties was: 87% recovery of surface area and 63% of average pore diameter when the fresh catalyst and improved 203% in the fracture resistance was achieved. These data indicated that the optimum concentration opened and increased catalyst pore diameter, surface area and mechanical strength. By increasing the acid concentration, the reactivated catalyst properties were much lower than those of the fresh catalyst, indicating that the characteristics are dependent on the contents of metals Mo, Ni and Al removed. The results on HDS activity suggest that the contaminating metals and coke are the factors causing the deactivation. The amount of active metals Mo and Ni remaining in the pellets were distributed when leaching was verified to an optimum value in the Mo/Ni ratio of 1.5. The hydrogenation activity was better in the reactivated catalyst than in fresh and deactivated catalysts.
Zhao et al (10) reported an alternative method (reactive solvent extraction) for rejuvenating deactivated hydroprocessing catalysts using hydrogen donor solvents. This alternative treatment may be in situ or ex-situ reactor according to the author, and its application is recommended primarily in cases where conventional regeneration is not a viable alternative to apply.
This study considers previous work with solvents, where hetero atomic solvents such as pyridine and quinoline were not suitable for the removal of carbon due to its adsorption on the catalyst surface. The use of gas oil as a solvent has an adequate performance only in the removal of carbon deposited in the early stages of catalyst operation, but this does not occur during removal of carbon deposited on catalysts with long operation. The use of solvents with the ability to donate hydrogen to promote the conversion of coke, has proven to be a good alternative for the recovery of catalytic activity.
Extraction studies on deactivated hydroprocessing catalysts were carried out with the following solvents: hydrotreated gas oil, 1234 tetrahydro naphthalene (THN) and a mixture of THN/pyrene at 400° C. and a hydrogen pressure of 10 MPa, in order to remove carbon on the catalyst surface and rejuvenating catalyst activity. The reactive extraction with solvents removes partially carbon deposited on the catalyst surface, presenting the following order of effectiveness for extraction: gas oi\ THN\ THN-pyrene. THN shows a much higher capacity than gas oil for the removal of carbon by donating hydrogen in situ for hydrogenating coke.
1234 tetrahydro naphthalene, dihydropyrene, and hexahydropyrene exhibit high ability to donate hydrogen, so mixed solvent systems donors and acceptors of hydrogen as THN-pyrene show some synergism in the conversion of carbon that is deposited in the deactivated catalysts; and pyrene has the capacity to exchange hydrogen and form hydropyrenes. The results showed 35% removal of carbon deposited on the catalyst when dealing with mixed solvent (THN/pyrene) resulting in the recovery of activity of up to 92% over the fresh catalyst.
Concluding that during gasoil hydroprocessing, loss of activity is proportional to the concentration of carbon in the catalyst, it is dominant in activity loss and severely reduces the half-life of the catalyst. The regeneration of these catalysts by methods comprising the deposited coke burning may damage, among other properties, the mechanical strength of the catalyst pellets.
Dehgani and colleagues (11) reported a method to solve the environmental problem that refineries have due to deactivated catalysts. They proposed returning these catalysts to the process by regeneration and rejuvenation. In the article, they presented an experimental study to recover the activity of a deactivated catalyst, in a hydrocracking unit, contaminated with metals and considered as non-regenerable, in order to reuse it in a process unit of HDT of kerosene.
During the experiment, they used two types of deactivated catalysts that contained residual oil of the process, taking as a base catalyst a NiW/SiO2-Al2O3 extruded for hydrocracking service. The method started by washing with naphtha the hydrocarbon that has the deactivated catalyst and then subjected to drying. Among the physicochemical properties analyzed of the fresh and deactivated washed with naphtha catalysts, it was reported that: The mechanical strength of the extrudate did not present significant changes while the metals that were deposited on the surface of the deactivated catalyst caused an increase in density and a decrease in surface area. The pore volume decreased by more than 20%. These data indicated that the catalyst was deactivated by pore blockage and contamination of the active sites with coke and metal contaminants. Although coke was removed by calcination in air, the metal remained in the pores.
Rejuvenation consisted on removing the metals deposited in the catalyst washed with naphtha using acetic acid and oxalic acid in Soxhlet apparatus. Subsequently, the treated catalyst is subjected to a process of removing carbon in a rotary horizontal furnace using air and controlling the temperature in the range of 400-700° C. They noted that 500° C. for 5 hours are the best conditions, based on the carbon content and surface area.
The deactivated catalyst had low levels of Fe and Na and minimum V. During leaching, different concentrations of acetic acid (0.1, 0.05 and 0.01 normal) and oxalic acid (0.1, 0.01 and 0.001 normal) were used. With leaching, there was an improvement in the surface area and pore volume because with such a process, pollutants are removed and the pores are opened. From the test HDT of kerosene, it was concluded that, except for the flash point (which is modifiable), the other properties of the product are in accordance with the specifications of kerosene. The most favorable value of HDS was achieved at temperature=300° C.; pressure=35 bar and H2/HC=100.
Souza et al (12) published an article about the importance of pre-treating deactivated hydrotreating catalysts for metal recovery. The paper applies three-step pretreatment for commercial deactivated catalysts NiMo/gamma-alumina type. Soluble coke extraction is made with n-hexane, and the attack of contaminants is done with oxalic acid. When deactivation is reversible, it is possible to restore much of the original activity of the catalyst by removing the deactivating agent or eliminating its effects in the active phase. There are few studies on treatment of coke soluble with solvents and treatment of attack known as “leaching” of pollutants' cover.
For this work two samples of deactivated diesel hydrodesulfurization catalysts, operated for 4 years in two units of hydrotreating heavy gas oil/diesel at a refinery in Brazil were used. Among the metals detected by X-ray fluorescence in these catalysts are iron, calcium and arsenic (Fe, Ca and As), which are not found in the fresh catalysts.
In order to remove the soluble carbon, this author recommends making a Soxleth extraction using 50 grams of the deactivated catalyst in contact with n-hexane for 6 hours. After this treatment, the recovered solvent is evaporated in a rotary evaporator and the organic phase removed from the catalyst is recovered. As a second step, the catalyst sample extracted (5 grams) is washed with 50 ml of aqueous oxalic acid solution, under stirring at 200 RPM at temperatures of 25, 50 and 75° C., times of 30, 60 and 90 minutes, to a variable concentration of oxalic acid (0.04, 0.08 and 0.12 moles per liter). According to the results obtained at 25° C. there are not many differences in the concentration of oxalic acid used, but the intermediate value of 0.08 mol/L is taken as the optimum.
Differences Between Patenting Procedure and Reports
Unlike the procedures used to rejuvenate hydroprocessing catalyst (1,2) of heavy hydrocarbon oil, that use solutions of inorganic acid H2SO4 type diluted to 15%, this invention does not apply it due to the environmental risks and corrosion that can result in the industrial unit. These treatments that are necessary to remove metal contaminants such as [Ni+V] in hydrotreating catalysts waste are not required in this new invention.
Unlike the cleaning treatment recommended for deactivated catalysts of emissions reduction (5) in automobiles, the mixture of the present invention contains various solvents, in different volumetric ratios. The only similarity is the iso-propanol component, which is used 20 volume % in this treatment, while in our invention is used only 15 volume %. The application reported for the cleaning reduction catalyst of reduction deactivated emissions is used for fuel switching with this solvent mixture in the engine of the vehicle at high temperature combustion and in the case of our invention is carried out at 50° C. in liquid phase.
Compared with application patent (6), which presents the catalyst cleaning using different solvents, this action is sequentially, meaning using a pure solvent each time. The solvents used do not correspond to those employed in this patent employs, and as part distinctive to the procedure are protecting, it is that in our case: we do not regenerate the catalyst with oxygen at temperatures of 350-500° C. When coke burning is carried out in-situ in the reactor leads to corrosion and contamination of the catalytic bed and the total elimination of metal sulfides, active HDS sites.